Tire molds for producing pneumatic vehicle tires are typically constructed of steel or aluminum, and are heated by steam heated platens or by placing the molds in steam domes. Thermal conduction is usually relied upon to transfer heat to the tread and sidewall forming surfaces, though heat pipes may also be used. The mold typically includes upper and lower sidewall forming parts and a segmented treadmolding ring. The segments of the treadmolding ring are affixed to “sliding shoes” which are in turn attached to guide mechanisms on a conical inner surface of an actuating ring such that the treadmolding segments move radially inwardly when the actuating ring is lowered.
Sheets of lubricating “sliding material” are mounted on the actuating ring's conical inner surface to facilitate smooth movement of the treadmolding ring segments during opening and closing of the mold. The sliding material is typically formed into a thin sheet and consists of two layers. A base layer, usually made of steel, provides support and faces the conical inner surface of the actuating ring. A top lubricating layer, made of a bronze composition, is used to facilitate the movement of the treadmolding segment and faces the treadmolding ring segments.
The high forces exerted upon the treadmolding segments as they are moved by the actuating ring, combined with the repetitive action of the tire mold in a production environment, causes the relatively soft lubricating layer of the sliding material to quickly wear. In view of this problem, a plurality of individual “wear plates” have been used wherein segmented portions of the sliding material are disposed about the conical inner surface of the actuating ring. The wear plates may be periodically inspected and individually replaced as needed. Examples of prior tire molds are taught by Hilke et al. in U.S. Pat. No. 4,741,683 and Steidl et al. in U.S. Pat. No. 6,413,068.
It is desirable to maximize heat conduction to the tread and sidewall forming portions of a tire mold. If the thermal conduction properties of the mold are less than optimum, the cure time for the tires will increase due to the additional time required to restore the mold to the proper curing temperature following a tire loading or unloading cycle. This results in reduced production capacity for the mold. Inefficient thermal conduction can also cause difficulty in providing temperature uniformity within the mold. For example, the air gaps surrounding the wear plates of prior art molds have a lower thermal conductivity than the wear plates themselves. These air gaps can result in nonuniform thermal conductivity and impede the transfer of heat to the tread forming portions of the mold. A wear plate is needed that will provide better, more uniform thermal conductivity between the actuating ring and the segmented treadmolding ring in order to improve heat transfer to the treadmolding surfaces.